Several scoring systems have been developed previously, which rely on radio transmission. These can be divided into those which require equipment on both missile and target (called cooperative systems) and those which are accommodated entirely on the target (called non-cooperative systems) where the missile behaves as a passive reflector or scatterer. The invention is concerned with non-cooperative systems.
U.S. Pat. No. 4,057,708 discloses a known non-cooperative system which measures the minimum miss distance and three dimensional coordinates of a missile trajectory with respect to a target in the form of an aircraft. This system uses pulses having a duration of 40 nanoseconds. Each transmitted pulse is derived by gating a continuously running oscillating signal so the transmitted pulse consists of several oscillations. The pulses reflected by the missile are received by a receiver on the aircraft, but accurate detection of missile presence is not possible, firstly because of multipath effects due to reflection from the aircraft skin and secondly because of the difficulty of correctly identifying the received signal with the multiple scatterers on the missile, such as nose fins or tail wings. The nature of the transmitted pulse does not enable these different features to be resolved.